1. Field of the Invention
The present invention relates to an image sensor. An image sensor according to the present invention is employed in an image scanner which is connected to a word processor, a personal computer or the like.
2. Description of the Prior Art
FIG. 19 is a sectional view showing a configuration of a conventional contact type image sensor.
The contact type image sensor is provided with an open-top unit housing 1 which has a light emitting diode array 2 serving as a light source arranged in a direction orthogonal to paper feeding directions A (i.e., a direction orthogonal to a face of drawing) on one side of the unit housing 1 and a photodiode array substrate 3 and a substrate 5 mounting a driving IC 4 which are stuck horizontally on a single supporting type insulating substrate 6. Both the substrates 3 and 5 are connected to each other to transmit a photodiode array driving signal from a chip of the driving IC 4 through a bonding wire 7, and the connection and the IC chip 4 are covered with protecting resin 8 or the like.
The top of the unit housing 1 and the upper surface of the photodiode array substrate 3 are covered with fiber plates 9 and 10 for transmitting and guiding light.
Japanese Unexamined Patent Publication Nos. 288056/1989 and 125168/1989 disclose image sensors in which a photodiode array substrate and a driving circuit substrate for the same are electrically connected by an elastic connector.
In the above-mentioned prior arts, the photodiode array substrate 3 and the driving IC mounting substrate 5 are fixed to the single insulating substrate 6.
For the reason, when defects of elements in the photodiode array are found or unsatisfactory conditions are caused in the wire bonding 7 and IC 4 after the unit is assembled, only defective parts of the photodiode array substrate 3, IC 4, IC mounting substrate 5 and supporting substrate 6 cannot be replaced with new ones.
Allowing for wire bonding, it is desirable that bonding pads of the photodiode array and IC bonding pads are arranged in horizontal direction to keep the resultant difference in level approximately an amount corresponding to the thickness of the IC 4.
However, when the photodiode array substrate 3 and the IC mounting substrate 5 are horizontally arranged, the contact type image sensor unit 1 has the problem that the unit width is larger in the paper feeding direction A in external dimensions because the photodiode array substrate 3 and the IC mounting substrate 5 are disposed along the paper feeding direction A.